Many liquid-liquid separation processes involve the separation of water from an organic phase. In such liquid-liquid separation processes, the formation of an aqueous phase that is immiscible with the organic phase allows for separation of the two phases to take place from one another by a variety of means. In particular, the immiscibility of water with the organic phase promotes partitioning between the aqueous phase and the organic phase.
The separation of water from an organic phase can be much more complicated when the water is present in an emulsified form within the organic phase, particularly when processing a water-in-oil emulsion. In such an emulsion, normal gravitational separation of the two phases does not occur by partitioning, or the partitioning process is so slow that it is operationally limiting.
One way to promote breaking of emulsions so that partitioning occurs more readily is through adding various emulsion-breaking substances, such as surfactants, pH modifiers, salts and the like, to the emulsion. Using these substances, however, increases the cost of processing the emulsion and impacts downstream operations. For example, using a surfactant to break water-in-oil emulsions may require removal of the surfactant from the organic phase before the organic phase is further processed. In another example, the use of a pH modifier to break a water-in-oil emulsion can also require further modifying the pH of the separated aqueous phase so that it may be suitably disposed of or further processed.
It is also costly to break emulsions using heat. Heating approaches are prohibitively expensive for many applications in which large fluid volumes are processed.
Other techniques for breaking emulsions include applying a centrifugal force to the emulsion. The application of centrifugal force to an emulsion results in coalescence of the small water droplets in the emulsion until the coalesced droplets increase sufficiently in size to form a bulk aqueous phase, also referred to as a continuous aqueous phase. Because of water's high mobility, it proceeds readily to the outer walls of a vessel in which a centrifugal force is being applied, while a water-depleted and less mobile organic phase remains more toward the longitudinal center of the vessel. This allows for a location-based separation of the two phases to take place.
The application of an electric field to an emulsion also promotes the coalescence of small water droplets into larger water droplets that more readily form a bulk aqueous phase. U.S. Pat. Nos. 6,136,174 and 8,591,714 describe processes and equipment for separating emulsions through application of an electric field to the emulsion. The dewatering processes disclosed in these patents, however, are limited in the extent of dewatering that they provide.
Many applications and processes can benefit from utilizing organic phases having lower water contents than presently available high-flux dewatering techniques provide. Lower flux and more costly dewatering techniques are typically required when an organic phase having a particularly low water content is needed for a specific application or process.